Metallized films are commonly produced for a variety of applications in which high-reflectivity of light is desirable, such as decorative, packaging and low-emissivity applications, for example. In conventional metal-flake pigment technology (such as in the production of vacuumbased aluminum pigments), a polymer film web is coated with a dissolvable polymer layer at atmospheric conditions and a nano-thick aluminum layer is deposited over it in a vacuum chamber. This process may be repeated several times on one or both sides of the web before the aluminum is removed from the web and reduced to a nano-flake pigment in a solvent bath, while the polymer film web is discarded (see for example EP0081599 and WO2014042639).
Polymer/aluminum multilayer structures may also be produced entirely in a vacuum chamber by depositing both materials in successive layers. Such structures have been used advantageously in the past to produce aluminum pigments in powder form, where the polymer is retained with the aluminum particle (see, for example, U.S. Pat. No. 5,912,069; and A. Yializis, et al., “Low Emissivity Polymer-Metal Pigments and Coatings,” 1997 Meeting of The IRIS Group On Camouflage Concealment and Deception, Volume 1, October 1997).
U.S. Pat. No. 7,754,106, teaches the production of metal oxide flake material by forming multilayer structures of release and metal oxide layers, where the release layer is formed by flash evaporating a monomeric liquid material that is deposited on a substrate as a liquid and then, using electron beam and/or plasma radiation, converted into a dissolvable solid. U.S. Pat. No. 6,398,999 and U.S. Pat. No. 7,820,088 teach a multilayer layer structure, in which the release layer is made of a thermoplastic material produced by thermal decomposition of polymers (such as acrylic and styrene resins) and polymerization using electron beam. Decomposition of a resin results in the deposition of random polymer fragments that form a layer that can be dissolved in a solvent, but it also results in many lower molecular weight gaseous products that impact the level of vacuum in a chamber, thus resulting in release coatings that are difficult to control and implement on large scale. US 20020041047 claims deposition of polymerizable and non polymerizable liquids that are partially polymerized on the surface before deposition of a flake layer. U.S. Pat. No. 8,852,476 asserts the use of polymerizable liquid release layers that partially polymerized on the surface by the heat of condensation of a metal layer.
With all diversity of disclosed processes of fabrication, there remain unaddressed practical problems stemming from inability of the existing methodologies to repeatedly produce flat and highly reflective flakes, the degradation of the flakes reduced from a multilayered structures formed in vacuum with no in-line passivation, safety issues accompanying the handling of flakes that contain non-passivated metal (such as aluminum), as well as defects of the flake material caused by the lack of such in-line passivation and those manifesting in “conglomeration” of “stacking” of the flake elements remaining not separated from one another.
The present invention is directed at providing solutions to at least some of these problems by further defining the types and chemistry of release materials that can be effectively dissolved in the process of production of individual flakes, as well as the thickness of such materials and process conditions required for production of flakes with high specular reflectivity and high corrosion resistance.